New bond of stone is completely crowding out other tank keystones.

I don't think so.

• http://vignette1.wikia.nocookie.net/leagueoflegends/images/c/cc/Bond_of_Stone_mastery_2016.png/revision/latest/scale-to-width-down/64?cb=20170218043831 Bond of Stone will surely be overused at the begin because it's new, but this keystone is aimed to those Tanks that don't really need to stay on the offense and just want to set up kills and help team mates (Taric works perfectly with it).

• http://vignette2.wikia.nocookie.net/leagueoflegends/images/a/a7/Courage_of_the_Colossus_mastery_2017.png/revision/latest/scale-to-width-down/64?cb=20170119020805 Courage of the Colossus is more for aggressive tanks or bruisers that want a shield in order to initiate or survive the first burst of incoming damage.

• http://vignette2.wikia.nocookie.net/leagueoflegends/images/c/cc/Grasp_of_the_Undying_mastery_2016.png/revision/latest/scale-to-width-down/64?cb=20170218043628 Grasp of the Undying instead works for the tanky guys that want more self sustain and survive prolonged fights.

Edit: Grasp might need some tweaking but overall the 3 Keystones are well diversificated.

maybe if grasp didn't suck mundo and other bruisers would use it

I mean... I does deserve it's time in the lime light. It's not like it's been good for at least like 6 months or longer. Though it does look... REALLY good.

yes, this yet-to-be released keystone is completely crowding out all other options

I doubt that. Even though Grasp needs a massive buff, that still wouldn't force everyone to take Bond of Stone because many other people would prefer to take Courage of the Colossus. Bond of Stone might become an issue in pro play though.